The preservation of sharp edges is important for many products and industries. Many industrial blades and medical tools are only useful if their sharp edges can be maintained for reasonably long periods of time. The sharpness is the result of the precision of the edge formed by the substrate and any coatings thereon. Razor blades, for example, have an edge formed by producing a radius of curvature at the blade's extreme tip from about 75 to about 1000 angstroms.
Corrosive and/or errosive forces can cause precision edge degradation. Razor blades, for example, dull considerably after first use.
The corrosive and/or errosive forces cause cracks, chips or breaks at the edge causing a jagged edge. For razor blades, the degradation of the precision edge causes increased friction and user discomfort. To overcome these problems the steel used for razor blades is therefore often coated first with a sputtered hard metal coating, followed by a coating of polytetrafluoroethylene (PTFE). The PTFE coating is usually tens to thousands of angstroms thick, and it is substantially removed from the blade upon first use. Enough PTFE survives to provide a measure of continued lubrication. However, the PTFE coatings do not prevent the degradation of the precision edge.
Also depositing of hard coatings is not entirely effective in preserving edge integrity. For example, a coating of platinum, titanium, chromium, chromium oxide or chromium nitride may be applied to a cutting edge to prolong its life. However, such hard coatings do not overcome the problem of corrosion that occurs at the grain boundary and corrosion that forms between the coating and the substrate.
Self-assembled monolayers have attracted attention in many areas because of the versatility they provide for surface modification. Self-assembled monolayers are highly ordered molecular assemblies that form spontaneously by chemisorption of functionalized molecules on a variety of substrates. The self-assembled monolayers as the name implies are very thin and of molecular thickness and their robustness and durability is questionable. They are often used in electronic applications to adhere dissimilar materials such as electrically conductive and dielectric layers. In such an application robustness and durability is not critical.